This invention relates to a laser beam device for motor vehicles including at least one transmitter, at least one receiver and a resolving lens system for laser beams, by means of which an area situated in front of the motor vehicle can be scanned while being divided into several explored areas.
In the case of known devices of this type, adjacent explored areas adjoin one another in a seamless manner as in German Patent document DE 37 01 340 A1. Alternatively, the adjacent explored areas have blanking gaps as described in German Patent document DE 40 28 788 A1; that is, the explored areas are positioned so as to fill gaps and have areas which are situated in-between and cannot be seen.
In order to obtain a relatively large azimuthal resolution area, it is required, in the case of the known devices, to provide a plurality of channels as in German Patent document DE 37 01 340 A1 or, as the result of the blanking gaps, problems arise with respect to recognizing narrow objects as in German Patent document DE 40 28 788 A1.
There is therefore needed a laser beam device of the abovementioned type which achieves a high resolution with minimal constructive expenditures.
These needs are met according to the present invention by a laser beam device for motor vehicles including at least one transmitter, at least one receiver and a resolving lens system for laser beams, by means of which an area situated in front of the motor vehicle can be scanned while being divided into several explored areas. Marginal areas adjoin a central area on both sides. The explored areas of these marginal areas overlap that of the central area.
If the central area and the two marginal areas have, for example, a field of view of 3.degree., and mutually overlap by one third respectively, an angular resolution of 2.cndot.2.degree. for the marginal areas and 3.cndot.1.degree. for the central area in the case of a total field of view of 7.degree. is obtained. In the case of a separate arrangement of explored areas, as described in the first-mentioned document above, these geometrical conditions can only be achieved using five areas and, therefore, in a pertaining analysis circuit having five channels. The advantage of avoiding blanking gaps achieved in comparison to the second document mentioned above becomes noticeable particularly in the case of obstacles which are situated in the proximity of the central area, that is, when the motor vehicle is driving straight ahead, specifically in the area of the driving corridor.
In a further embodiment of the basic idea of the present invention, the field of view can be enlarged without gaps and with a good azimuthal resolution if the beam geometry is properly selected such that the marginal areas are adjoined by outer areas whose explored areas overlap with that of the respective marginal area but not with that of the central area. In the case of movement of the object across the individual channels, there is the possibility of precisely following this movement and, thus, predicting with high precision the probable course of the path of movement. Such movement will take place, for example, when an object passes through several explored areas because of the movement of the motor vehicle. By referring to the self-movement of the motor vehicle, the self-movement of the object can be determined and a dangerous situation which arises can be prevented by corresponding countermeasures. At a minimum, its danger can at least be reduced. Such countermeasures may be carried out in an active manner, that is, for example, by an automatic reduction of the driving torque of the internal-combustion engine or the initiating of a braking operation, or in a passive manner, by use of an acoustic or visual reference to the imminent danger.
The basic idea of the invention, that is, achieving a relatively high (fine) resolution by the relatively large solid angle of the individual explored area with the simultaneous overlapping of adjacent explored areas, may also be used for providing the explored area with an overall large size. For this purpose, the field of view of the outer area is larger than that of the marginal area. This has the aim of keeping the solid angle larger in the outer area than for the explored areas in the center or in the marginal area. Since the movement of an object with respect to the motor vehicle can be detected at low expenditures, as indicated above, the dangerousness of an object can also be recognized in the case of a correspondingly large solid angle for the outer area. If this object, for example, does not enter the adjacent marginal area, there is probably no danger of collision.
To take this outer area into account is particularly advantageous when the speed of the motor vehicle is relatively low, for example, 30 km/h. The outer area is important only for such low speeds, while it does not have to be taken into account at high speeds, for example, 100 km/h. This also applies specifically when the outer area has a solid angle which is significantly larger than the solid angle of the central area or of the two marginal areas. 6.degree. may be useful as the value for this solid angle and may be advantageous with respect to the indicated example. The energy which is beamed into this outer area may be identical to the energy which reaches the central area. Thus, the energy apportioned to the solid-angle unit will be less. As the result of the shorter distance of the objects which are of interest--objects at a large distance outside the central area do not have to be taken into account--the received backscattered energy remains approximately identical to that of objects in the central area which are at a larger distance.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.